I know what you mean, I've had ectopics for ummmmm 30 years now and they still scare me when I get an 'odd run' like the set today, very very occasionally. I am used to them all the time, most days, but like you this felt 'different' and 'worse'. I had a similar event to you last year, sudden fast racing, felt dizzy and fainty, the room span and I thought I was going to fall over. Thinking about it afterwards, analysing it to try and reassure myself, I felt the fast race bit of the heart catching up after a missed beat and entered an instant 'panic/something is wrong/send adrenaline out asap mode' within a split second and that caused the second part of the symptoms. So, I'm just saying it is definitely true that an instant fear response can cause the blurring/spinning room thing. If you are a pesron, like myself, who can cough and do postural things to alter your heart patterns, then it sounds like you are triggering your vagus nerve (near the stomach) and it could be that the exercises you were doing did just that - triggered it.